Braking control valves are well known in the prior art, as illustrated for example in the patent documents U.S. Pat. Nos. 4,615,566, 4,624,507, and EP 0 223 641, and enable a modified braking pressure to be developed at their outlet and applied to the rear brakes of a motorised vehicle which is related to the braking pressure applied both to their inlet and to the front wheels of the vehicle, but is nonetheless lower than the front wheel braking pressure at values greater than a defined threshold value.
One of the problems encountered in the design of such control valves resides in the difficulty of obtaining the desired variation of the outlet pressure relative to the inlet pressure and, more precisely, of avoiding that the relationship between the outlet pressure and the inlet pressure contains an anomaly, or "flat", corresponding to a more or less local defect in the variation of the outlet pressure.